Have you heard the one about the Englishman, the Irishman and the Scotsman?

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IDIOMS

- be (a) one for (doing) sth

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GRAMMAR

one

One / ones is used to avoid repeating a countable noun, but there are some times when you should not use it, especially in formal speech or writing:

1 After a possessive ( my , your , Mary's , etc.), some , any , both or a number, unless it is used with an adjective:

'Did you get any postcards?' 'Yes, I bought four nice ones.'

• I bought four ones.

2 It can be left out after superlatives, this , that , these , those , either , neither , another , which , etc.:

'Here are the designs. Which (one) do you prefer?' 'I think that (one) looks the most original.'

3 These ones and those ones are not used in NAmE , and are unusual in BrE :

Do you prefer these designs or those?

4 It is never used to replace uncountable nouns and is unusual with abstract countable nouns:

The Scottish legal system is not the same as the English system

, is better than

...as the English one.

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WORD ORIGIN

Old English ān , of Germanic origin; related to Dutch een and German ein , from an Indo-European root shared by Latin unus . The initial w sound developed before the 15th cent. and was occasionally represented in the spelling; it was not accepted into standard English until the late 17th cent.